Engineering Donor–Acceptor Heterostructure Metal–Organic Framework Crystals for Photonic Logic Computation

Integrating Full-Color 2D Optical Waveguide and Heterojunction Engineering in Halide Microsheets for Multichannel Photonic Logical Gates

Ensuring information security has emerged as a paramount concern in contemporary human society. Substantial advancements in this regard can be achieved by leveraging photonic signals as the primary information carriers, utilizing photonic logical gates capable of wavelength tunability across various time and spatial domains. However, the challenge remains in the rational design of materials possessing space-time-color multiple-resolution capabilities. In this work, a facile approach is proposed for crafting metal-organic halides (MOHs) that offer space-time-color resolution. These MOHs integrate time-resolved room temperature phosphorescence and color-resolved excitation wavelength dependencies with both space-resolved ex situ optical waveguides and in situ heterojunctions. Capitalizing on these multifaceted properties, MOHs-based two-dimensional (2D) optical waveguides and heterojunctions exhibit the ability to tune full-color emissions across the spectra from blue to red, operating within different spatial and temporal scales. Therefore, this work introduces an effective methodology for engineering space-time-color resolved MOH microstructures, holding significant promise for the development of high-density photonic logical devices.

Switchable Anisotropic/Isotropic Photon Transport in a Double-Dipole Metal-Organic Framework via Radical-Controlled Energy Transfer

Directional control of photon transport at micro/nanoscale holds great potential in developing multifunctional optoelectronic devices. Here, the switchable anisotropic/isotropic photon transport is reported in a double-dipole metal-organic framework (MOF) based on radical-controlled energy transfer. Double-dipole MOF microcrystals with transition dipole moments perpendicular to each other have been achieved by the pillared-layer coordination strategy. The energy transfer between the double dipolar chromophores can be modulated by the photogenerated radicals, which permits the in situ switchable output on both polarization (isotropy/anisotropy state) and wavelength information (blue/red-color emission). On this basis, the original MOF microcrystal with isotropic polarization state displays the isotropic photon transport and similar reabsorption losses at various directions, while the radical-affected MOF microcrystal with anisotropic polarization state shows the anisotropic photon transport with distinct reabsorption losses at different directions, finally leading to the in situ switchable anisotropic/isotropic photon transport. These results offer a novel strategy for the development of MOF-based photonic devices with tunable anisotropic performance.

Modular Gating of Ion Transport by Postsynthetic Charge Transfer Complexation in a Metal-Organic Framework

Nature's design of biological ion channels that demonstrates efficient gating and selectivity brings to light a very promising model to mimic and design for achieving selective and tunable ion transport. Functionalized nanopores that permit modulation of the pore wall charges are a compelling approach to gain control over the ion transport mechanism through the pores. This makes way for employing a noncovalent supramolecular approach for attaining charge reversal of the MOF pore walls using donor-acceptor pairs that can demonstrate strong charge transfer interactions. Herein, robust Zr4+-based mesoporous MOF-808 was postsynthetically modified into an anion-selective nanochannel (MOF-808-MV) by modification with dicationic viologen-based motifs. Charge modulation and even reversal of the MOF-808-MV pore walls were then explored taking advantage of strong charge transfer interactions between the grafted dicationic viologen acceptor moieties and anionic, π-electron-rich donor guest molecules such as pyranine (PYR) and tetrathiafulvalene tetrabenzoic acid (TTF-TA). Tunability of the MOF pore charge from positive to neutral to negative was achieved via simple methodologies such as diffusion control in case of guest molecule like PYR and by pH modulation for pH-responsive guest like TTF-TA. This results in a concomitant modulation in the selectivity of the nanochannel, rendering it from anion-selective to ambipolar to cation-selective. Furthermore, as a real-time application of this ion channel, Na+ ion conductivity (σ = 3.5 × 10-5 S cm-1) was studied at ambient temperature.

Naphthalenediimide/Iodobismuthate Hybrid Heterostructures: Water Resistance and Long-Lived Charge-Separated States

Organic-inorganic hybrid iodobismuthate perovskites have become promising semiconductive materials for their environmentally friendly and light-harvesting characteristics. However, their low-dimensional bismuth-iodide skeletons result in poor charge-separation efficiency, limiting their application in optoelectronic devices. To address this issue, the donor-acceptor (D-A) heterostructures have been introduced to the iodobismuthate hybrid materials by incorporating an electron-deficient N,N'-bis(4-aminoethyl)-1,4,5,8-naphthalene diimide (NDIEA) as the electron acceptor and organic counterpart. Five naphthalenediimide/iodobismuthate hybrid heterostructures, named (H2NDIEA)1.5·Bi2I9·3DMF (1), H2NDIEA·[Bi2I8(DMF)2]·2DMF (2), (H2NDIEA)2·Bi4I16·2H2O·4MeOH (3), (H2NDIEA)2·Bi4I16·8H2O (4), and [(H2NDIEA)2·Bi6I22]n·4nH2O (5) (DMF = N,N-dimethylformamide), were synthesized. Their crystal structures, water stabilities, charge-separated behaviors, and electrical properties have been studied through experimental and computational investigations. The results revealed that hybrids 3-5 exhibited high water resistance attributed to their tightly packed structures and robust H-bonds between solvent molecules and organic-inorganic supramolecular frameworks. Density functional theory calculations confirmed characteristic type-IIa band alignments of all the five hybrids, facilitating to the photoinduced charge separation. Moreover, the closer contact caused by the strong anion-π interactions between electron donors and acceptors in hybrid 5 leads to the long-lived charge-separated states and improved electrical properties compared to the other hybrids.

Organic Bilayer Heterostructures with Built-In Exciton Conversion for 2D Photonic Encryption

Organic multilayer heterostructures with accurate spatial organization demonstrate strong light-matter interaction from excitonic responses and efficient carrier transfer across heterojunction interfaces, which are considered as promising candidates toward advanced optoelectronics. However, the precise regulation of the heterojunction surface area for finely adjusting exciton conversion and energy transfer is still formidable. Herein, organic bilayer heterostructures (OBHs) with controlled face-to-face heterojunction via a stepwise seeded growth strategy, which is favorable for efficient exciton propagation and conversion of optical interconnects are designed and synthesized. Notably, the relative position and overlap length ratio of component microwires (LDSA /LBPEA = 0.39-1.15) in OBHs are accurately regulated by modulating the crystallization time of seeded crystals, resulting into a tailored heterojunction surface area (R = Loverlap /LBPEA = 37.6%-65.3%). These as-prepared OBHs present the excitation position-dependent waveguide behaviors for optical outcoupling characteristics with tunable emission colors and intensities, which are applied into two-dimensional (2D) photonic barcodes. This strategy opens a versatile avenue to purposely design OBHs with tailored heterojunctions for efficient energy transfer and exciton conversion, facilitating the application possibilities of advanced integrated optoelectronics.

Significant increase of the photoresponse range and conductivity for a chalcogenide semiconductor by viologen coating through charge transfer

Widening the photoresponse range while enhancing the electrical properties of semiconductors could reduce the complexity and cost of photodetectors or increase the power conversion efficiency of solar cells. Surface doping through charge transfer with organic species is one of the most effective and widely used approaches to achieve this aim. It usually features easier preparation over other doping methods but is still limited by the low physicochemical stability and high cost of the used organic species or low improvement of electrical properties. This work shows unprecedented surface doping of semiconductors with highly stable, easily obtained, and strong electron-accepting viologen components, realizing the significant improvement of both the photoresponse range and conductivity. Coating the chalcogenide semiconductor KGaS2 with dimethyl viologen dichloride (MV) yields a charge-transfer complex (CTC) on the surface, which broadens the photoresponse range by nearly 300 nm and improves the conductivity by 5 orders of magnitude. The latter value surpasses all records obtained by surface doping through charge transfer with organic species.

Spatially Resolved Organic Whispering-Gallery-Mode Hetero-Microrings for High-Security Photonic Barcodes

Whispering-gallery-mode (WGM) microcavities featuring distinguishable sharp peaks in a broadband exhibit enormous advantages in the field of miniaturized photonic barcodes. However, such kind of barcodes developed hitherto are primarily based on microcavities wherein multiple gain medias were blended into a single matrix, thus resulting in the limited and indistinguishable coding elements. Here, a surface tension assisted heterogeneous assembly strategy is proposed to construct the spatially resolved WGM hetero-microrings with multiple spatial colors along its circular direction. Through precisely regulating the charge-transfer (CT) strength, full-color microrings covering the entire visible range were effectively acquired, which exhibit a series of sharp and recognizable peaks and allow for the effective construction of high-quality photonic barcodes. Notably, the spatially resolved WGM hetero-microrings with multiple coding elements were finally acquired through heterogeneous nucleation and growth controlled by the directional diffusion between the hetero-emulsion droplets, thus remarkably promoting the security strength and coding capacity of the barcodes. The results would be useful to fabricate new types of organic hierarchical hybrid WGM heterostructures for optical information recording and security labels.

Directional Self-Assembly of Facet-Aligned Organic Hierarchical Super-Heterostructures for Spatially Resolved Photonic Barcodes

Organic multicolor heterostructures with spatially resolved luminescent colors and identifiable patterns have exhibited considerable potential for achieving micro-/nanoscale photonic barcodes. Nevertheless, such types of barcodes reported thus far are exclusively based on a single heterostructure with limited coding elements. Here, a directional self-assembly strategy is proposed to achieve high-coding-capacity spatially resolved photonic barcodes through rationally constructing organic hierarchical super-heterostructures, where numerous subheterostructure blocks with flat hexagonal facets are precisely oriented with their specific facets via a reconfigurable capillary force. The building blocks were prepared through a one-pot sequential heteroepitaxial growth, which enables the effective modulation of the structural and color characteristics in coding structures. Significantly, a directional facet-to-facet attraction between particles via facet registration leads to the formation of well-defined 1D super-heterostructures, which contain multiple coding elements, thus providing a good platform for constructing the high-coding-capacity photonic barcodes. The results may be useful in fabricating organic hierarchical hybrid super-heterostructures for security labels and optical data recording.

Photo-controllable heterostructured crystals of metal-organic frameworks via reversible photocycloaddition

Metal-organic framework (MOF)-based heterostructures are attractive because they can provide versatile platforms for various applications but are limited by complex liquid epitaxial growth methods. Here, we employ photolithography to fabricate and control MOF-based heterostructured crystals via [4 + 4] photocycloaddition. A layered dysprosium-dianthracene framework, [Dy(NO3)3(depma2)1.5]·(depma2)0.5 (2) [depma2 = pre-photodimerized 9-diethylphosphonomethylanthracene (depma)] underwent a single-crystal-to-single-crystal transition at 140 °C to form [Dy(NO3)3(depma)(depma2)]·(depma2)0.5 (3). The dissociated anthracene moieties are face-to-face π-π interacted allowing a reversible photocycloaddition between 2 and 3. This structural transformation causes a luminescence switch between blue and yellow-green and thus can be used to fabricate erasable 2 + 3 heterostructured crystals for rewritable photonic barcodes. The internal strain at the heterostructure interface leads to photobending and straightening of the crystal, a photomechanical response that is fast, reversible and durable, even operating at 140 °C, making it promising for photoactuation. This work may inspire the development of intelligent MOF-based heterostructures for photonic applications.

Water-Stable Cd-MOF with fluorescent sensing of Tetracycline, Pyrimethanil, abamectin benzoate and construction of logic gate

Due to the indiscriminate abuse of pesticides and antibiotics has caused serious threats to the environment and human and animal bodies, the detection of antibiotics and pesticides has attracted widespread attention in recent years. Herein, a novel 2D Cd (II)-MOF, [Cd(L)_0.5(1,2-bimb)] (Cd-L-1,2-bimb), [H₄L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 1, 2-bimb = 1, 2-bis[(1H-imidazol-1-yl) methyl] benzene] is synthesized. Cd-L-1,2-bimb has excellent stability in different organic solvents and in the range of pH 1.1-12.5. Cd-L-1,2-bimb exhibits high selectivity, high sensitivity, and fast luminescent response to pesticides [pyrimethanil (PTH, LOD = 2.2 μM) and abamectin benzoate (AMB, LOD = 2.39 μM)] and antibiotic contaminants tetracycline (TET, LOD = 0.13 μM). Cd-L-1,2-bimb displays discriminative fluorescence when detecting AMB and PTH, and is an implication logic gate. Finally, the possible detection mechanism of Cd-L-1,2-bimb toward different pollutants is also further investigated. This MOF-based multifunctional sensor opens up new prospects for environmental monitors.

Dynamic Epitaxial Growth of Organic Heterostructures for Polarized Exciton Conversion

Highly spatial and angular precision in epitaxial-growth process is crucial for constructing organic low-dimensional heterostructures (OLDHs) with the desired substructures, which remains significant challenge owing to the unpredicted location of complex heterogeneous nucleation. Herein, a dynamic epitaxial-growth approach is developed along the tailored longitudinal/horizontal directions to create diverse OLDHs with hierarchical architectures. The controlled morphology evolution of seed crystals from kinetic to thermodynamic species is achieved via incrementally increasing the crystallization time from 0 to 600 s. Accordingly, the kinetic and thermodynamic seed crystals respectively present the specific lattice-matching crystal-planes of (100) and (011), which facilitates the longitudinal epitaxial-growth (LG) process for triblock heterostructures, and the horizontal epitaxial-growth (HG) process for axial-branch heterostructures. The dominant core/shell heterostructures are prepared via both LG and HG processes with a crystallization time of ≈30 s. Significantly, these prepared OLDHs realize the rationally polarized exciton conversion for optical logic gate application through the exciton conversion and photon propagation at the heterojunction. This strategy provides an avenue for the precise synthesis of OLDHs with anisotropy optical characters for integrated optoelectronics.

Low-Dimensional Organic Crystals: From Precise Synthesis to Advanced Applications

Low-dimensional organic crystals (LOCs) have attracted increasing attention recently for their potential applications in miniaturized optoelectronics and integrated photonics. Such applications are possible owing to their tunable physicochemical properties and excellent charge/photon transport features. As a result, the precise synthesis of LOCs has been examined in terms of morphology modulation, large-area pattern arrays, and complex architectures, and this has led to a series of appealing structure-dependent properties for future optoelectronic applications. This review summarizes the recent advances in the precise synthesis of LOCs in addition to discussing their structure-property relationships in the context of optoelectronic applications. It also presents the current challenges related to organic crystals with specific structures and desired performances, and the outlook regarding their use in next-generation integrated optoelectronic applications.

Donor-Acceptor Hybrid Heterostructures: An Emerging Class of Photoactive Materials with Inorganic and Organic Semiconductive Components

Just as the heterojunctions in physics, donor-acceptor (D-A) heterostructures are an emerging class of photoactive materials fabricated from two semiconductive components at the molecular level. Among them, D-A hybrid heterostructures from organic and inorganic semiconductive components have attracted extensive attention in the past decades due to their combined advantages of high stability for the inorganic semiconductors and modifiability for the organic semiconductors, which are particularly beneficial to efficiently achieve photoinduced charge separation and transfer upon irradiations. In this review, by analogy with the heterojunctions in physics, a definition of the D-A heterostructures and their general design and synthetic strategies are given. Meanwhile, the D-A hybrid heterostructures are focused on and their recent advances in potential applications of photochromism, photomodulated luminescence, and photocatalysis summarized.

Tunable fluorescence emission based on multi-layered MOF-on-MOF

Luminescent metal-organic frameworks (MOFs) have garnered considerable attention in various fields. Herein, we proposed a hierarchical confinement strategy based on MOF-on-MOF to tune luminescence emission ranging from blue to red including white light in a flexible way. The easily available ZIF-8 MOF was used as a host for the confinement of two kinds of size-matching dyes (perylene and rhodamine B) to obtain a layered ZIF-8@dye@ZIF-8@dye via in situ encapsulation and seed-mediated synthesis. ZIF-8@dye@ZIF-8@dye materials with different fluorescence emission in dispersed and solid states were both obtained by tuning the initial encapsulation concentration of dye and changing the structure of the inner and outer ZIF-8@dye layers. To our delight, ZIF-8@0.125perylene@ZIF-8@25RhB with white light emission in the dispersed state was obtained; meanwhile, ZIF-8@0.125perylene + 25RhB and mechanically mixed ZIF-8@0.125perylene + ZIF-8@25RhB could not realize white light emission under the same conditions, indicating that the proposed hierarchical confinement strategy facilitated white light regulation. Similarly, the emission of ZIF-8@dye@ZIF-8@dye in the solid state has also been investigated; ZIF-8@perylene@ZIF-8@3RhB with white light emission was obtained, while white light emission could not be achieved in ZIF-8@perylene + 3RhB and ZIF-8@perylene + ZIF-8@3RhB, which further indicated the importance of the hierarchical confinement strategy based on MOF-on-MOF. The proposed hierarchical confinement strategy may also inspire the development of other functional optical MOF materials.

Lattice-mismatch-free growth of organic heterostructure nanowires from cocrystals to alloys

Organic heterostructure nanowires, such as multiblock, core/shell, branch-like and related compounds, have attracted chemists’ extensive attention because of their novel physicochemical properties. However, owing to the difficulty in solving the lattice mismatch of distinct molecules, the construction of organic heterostructures at large scale remains challenging, which restricts its wide use in future applications. In this work, we define a concept of lattice-mismatch-free for hierarchical self-assembly of organic semiconductor molecules, allowing for the large-scale synthesis of organic heterostructure nanowires composed of the organic alloys and cocrystals. Thus, various types of organic triblock nanowires are prepared in large scale, and the length ratio of different segments of the triblock nanowires can be precisely regulated by changing the stoichiometric ratio of different components. These results pave the way towards fine synthesis of heterostructures in a large scale and facilitate their applications in organic optoelectronics at micro/nanoscale.

The large-scale synthesis of organic heterostructure nanowires is challenging. Here, the authors report the synthesis of organic triblock nanowires via a lattice mismatch-free strategy.

An electron-deficient MOF as an efficient electron-transfer catalyst for selective oxidative carbon-carbon coupling of 2,6-di-tert-butylphenol

Naphthalene diimides (NDIs), a type of electron-deficient dye molecule with high quadrupole moment and excellent redox activity, have been utilized in various fields, such as energy transfer, chemical sensing, anion transport, and photo-/electrochromic materials. In this study, an electron-deficient metal-organic framework with one-dimensional channels, Eu₂(BBNDI)₃(DMF)₂ (MOF 1) (H₂BBNDI = N,N'-bis(3-benzoic acid)naphthalene diimide), was successfully constructed based on the naphthalene diimide derivative. Because of the generation of NDI radicals by electron transfer between components, this material exhibits fast-responsive reversible photochromic properties. Moreover, it shows high efficiency and selective oxidation of 2,6-di-tert-butylphenol to its quinone derivative, aldehyde, and dimeric or trimeric phenol derivative by controlling the reaction conditions.

Assembly and Applications of Macrocyclic-Confinement-Derived Supramolecular Organic Luminescent Emissions from Cucurbiturils

Cucurbit[n]urils (Q[n]s or CB[n]s), as a classical of artificial organic macrocyclic hosts, were found to have excellent advantages in the fabricating of tunable and smart organic luminescent materials in aqueous media and the solid state with high emitting efficiency under the rigid pumpkin-shaped structure-derived macrocyclic-confinement effect in recent years. This review aims to give a systematically up-to-date overview of the Q[n]-based supramolecular organic luminescent emissions from the confined spaces triggered host-guest complexes, including the assembly fashions and the mechanisms of the macrocycle-based luminescent complexes, as well as their applications. Finally, challenges and outlook are provided. Since this class of Q[n]-based supramolecular organic luminescent emissions, which have essentially derived from the cavity-dependent confinement effect and the resulting assembly fashions, emerged only a few years ago, we hope this review will provide valuable information for the further development of macrocycle-based light-emitting materials and other related research fields.

Donor–acceptor systems in metal–organic frameworks: design, construction, and properties

In this highlight, the development of donor acceptor (D–A) MOF was briefly reviewed and summarized in the aspects of design, construction, and properties. Also, an outlook about the research and potential application of D–A MOF has been presented.

Achieving a blue-excitable yellow-emitting Ca-LMOF phosphor via water induced phase transformation

The first blue-excitable calcium-based LMOF yellow phosphor is achieved via water induced phase transformation. The compound with high luminescence quantum efficiency can be coated directly onto a commercial blue LED chip to fabricate a white LED.

Photochromic Polyoxometalate/Perylenediimide Donor-Acceptor Hybrid Crystals with Interesting Luminescent Properties

The self-assembly of electron-deficient protonated N, N'-dipyridyltetrachloroperylenediimide (4Cl-DPPDI) and electron-rich polyoxometalate acids H_nXM₁₂O₄₀ (POMs; X = P or Si; M = W or Mo) resulted in four isomorphous donor-acceptor hybrid crystals 1-4 with segregated POM anions and one-dimensional racemic hydrogen-bonded 4Cl-DPPDI networks as electron-donor and -acceptor components, respectively. Because of the compact contacts between the POM anions and 4Cl-DPPDI tectons induced by anion-π interactions, besides enhanced photochromism, these four unique isostructural hybrids exhibited unusual room-temperature phosphorescence (RTP) emissions. More interestingly, owing to the facial compact contacts of two racemic 4Cl-DPPDI tectons induced by lone pair-π-assisted π-π interactions, they also showed unprecedented photon upconversion by triplet-triplet annihilation (TTA).

Recent advances in luminescent metal-organic frameworks and their photonic applications

In recent years, metal-organic frameworks (MOFs) have been attracting ever more interest owing to their fascinating structures and widespread applications. Among the optoelectronic materials, luminescent MOFs (LMOFs) have become one of the most attractive candidates in the fields of optics and photonics thanks to the unique characteristics of their frameworks. Luminescence from MOFs can originate from either the frameworks, mainly including organic linkers and metal ions, or the encapsulated guests, such as dyes, perovskites, and carbon dots. Here, we systematically review the recent progress in LMOFs, with an emphasis on the relationships between their structures and emission behaviour. On this basis, we comprehensively discuss the research progress and applications of multicolour emission from homogeneous and heterogeneous structures, host-guest hybrid lasers, and pure MOF lasers based on optically excited LMOFs in the field of micro/nanophotonics. We also highlight recent developments in other types of luminescence, such as electroluminescence and chemiluminescence, from LMOFs. Future perspectives and challenges for LMOFs are provided to give an outlook of this emerging field. We anticipate that this article will promote the development of MOF-based functional materials with desired performance towards robust optoelectronic applications.

Pyrene-Functionalized Fluorescent Nanojars: Synthesis, Mass Spectrometric, and Photophysical Studies

Nanojars are a class of supramolecular coordination complexes based on pyrazolate, Cu2+, and OH- ions that self-assemble around highly hydrophilic anions and serve as efficient anion binding and extraction agents. In this work, the synthesis, characterization, and photophysical properties of pyrene-functionalized fluorescent nanojars are presented. Three pyrene derivatives, 4-(pyren-1-yl)pyrazole (HL1), 4-(5-(pyren-1-yl)pent-4-yn-1-yl)pyrazole (HL2), and 4-(3-(pyrazol-4-yl)propyl)-1-(pyren-1-yl)-1,2,3-triazole (HL3), and the corresponding nanojars were synthesized and characterized using nuclear magnetic resonance spectroscopy and mass spectrometry. Electronic absorption, steady-state, and time-resolved fluorescence measurements were carried out to understand the interaction between the pyrene fluorophore and copper nanojars. Optical absorption measurements have shown minor ground state interaction between the fluorophore and nanojars. The fluorescence of pyrene is significantly quenched when attached to nanojars, suggesting strong contribution from the paramagnetic Cu2+ ions. Significant static quenching is observed in the case of L1, when pyrene is directly bound to the nanojar, whereas in the case of L2 and L3, when pyrene is attached to the nanojars using flexible tethers, both static and dynamic quenching are observed.

Manipulating spatial alignment of donor and acceptor in host-guest MOF for TADF

Thermally activated delayed fluorescence (TADF) was achieved when electron-rich triphenylene (Tpl) donors (D) were confined to a cage-based porous MOF host (NKU-111) composed of electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (Tpt) acceptor (A) as the ligand. The spatially-separated D and A molecules in a face-to-face stacking pattern generated strong through-space charge transfer (CT) interactions with a small singlet-triplet excited states energy splitting (∼0.1 eV), which enabled TADF. The resulting Tpl@NKU-111 exhibited an uncommon enhanced emission intensity as the temperature increased. Extensive steady-state and time-resolved spectroscopic measurements and first-principles simulations revealed the chemical and electronic structure of this compound in both the ground and low-lying excited states. A double-channel (T1, T2) intersystem crossing mechanism with S1 was found and explained as single-directional CT from the degenerate HOMO-1/HOMO of the guest donor to the LUMO + 1 of one of the nearest acceptors. The rigid skeleton of the compound and effective through-space CT enhanced the photoluminescence quantum yield (PLQY). A maximum PLQY of 57.36% was achieved by optimizing the Tpl loading ratio in the host framework. These results indicate the potential of the MOFs for the targeted construction and optimization of TADF materials.

Laterally Engineering Lanthanide-MOFs Epitaxial Heterostructures for Spatially Resolved Planar 2D Photonic Barcoding

Metal-organic frameworks (MOFs) heterostructures with domain-controlled emissive colors have shown great potential for achieving high-throughput sensing, anti-counterfeit and information security. Here, a strategy based on steric-hindrance effect is proposed to construct lateral lanthanide-MOFs (Ln-MOFs) epitaxial heterostructures, where the channel-directed guest molecules are introduced to rebalance in-plane and out-of-plane growth rates of the Ln-MOFs microrods and eventually generate lateral MOF epitaxial heterostructures with controllable aspect ratios. A library of lateral Ln-MOFs heterostructures are acquired through a stepwise epitaxial growth procedure, from which rational modulation of each domain with specific lanthanide doping species allows for definition of photonic barcodes in a two-dimensional (2D) domain with remarkably enlarged encoding capacity. The results provide molecular-level insight into the use of modulators in governing crystallite morphology for spatially assembling multifunctional heterostructures.

The Synthesis and Properties of TIPA-Dominated Porous Metal-Organic Frameworks

Metal-Organic Frameworks (MOFs) as a class of crystalline materials are constructed using metal nodes and organic spacers. Polydentate N-donor ligands play a mainstay-type role in the construction of metal-organic frameworks, especially cationic MOFs. Highly stable cationic MOFs with high porosity and open channels exhibit distinct advantages, they can act as a powerful ion exchange platform for the capture of toxic heavy-metal oxoanions through a Single-Crystal to Single-Crystal (SC-SC) pattern. Porous luminescent MOFs can act as nano-sized containers to encapsulate guest emitters and construct multi-emitter materials for chemical sensing. This feature article reviews the synthesis and application of porous Metal-Organic Frameworks based on tridentate ligand tris (4-(1H-imidazol-1-yl) phenyl) amine (TIPA) and focuses on design strategies for the synthesis of TIPA-dominated Metal-Organic Frameworks with high porosity and stability. The design strategies are integrated into four types: small organic molecule as auxiliaries, inorganic oxyanion as auxiliaries, small organic molecule as secondary linkers, and metal clusters as nodes. The applications of ratiometric sensing, the adsorption of oxyanions contaminants from water, and small molecule gas storage are summarized. We hope to provide experience and inspiration in the design and construction of highly porous MOFs base on polydentate N-donor ligands.

Progress in Multifunctional Metal-Organic Frameworks/Polymer Hybrid Membranes

The fabrication of state-of-the-art membranes with customized functions and high efficiency is of great significance, but presents challenges. Emerging metal-organic frameworks (MOFs)/polymer hybrid membranes have provided bright promise as an innovative platform to target multifunctional hybrid materials and devices; this is thanks to their unique properties, which come from three components that are collaboratively enforced. This minireview provides a brief overview of recent progress in the construction of such hybrid membranes, and highlights some of their very important applications in separation, conduction, and sensing.

Tetraphenylpyrazine-Based Manganese Metal-Organic Framework as a Multifunctional Sensor for Cu2+, Cr3+, MnO4-, and 2,4,6-Trinitrophenol and the Construction of a Molecular Logical Gate

A tetraimidazole-decorating tetraphenylpyrazine has been designed and utilized for the fabrication of a novel metal-organic framework (MOF), denoted as {Mn(Tipp)(A)₂}_n·2H₂O (TippMn, where Tipp = 2,3,5,6-tetrakis[4-[(1H-imidazol-1-yl)methyl]phenyl]pyrazine and A = deprotonation of 1,4-naphthalenedicarboxylic acid), through hydrothermal synthesis. Structural analysis reveals that TippMn possesses a 2-fold-interpenetrated 4,8-connected three-dimensional (3D) network with an unprecedented {4¹⁶·6¹²}{4⁴·6²} topology. Fluorescent spectral investigations indicate that TippMn shows discriminative fluorescence when treated by Cr³⁺ and Cu²⁺, giving an INHIBIT logical gate performance. Meanwhile, TippMn can be further used as a sensor for MnO₄^- and 2,4,6-trinitrophenol (TNP) by fluorescence quenching. Notably, the sensing processes toward Cu²⁺, Cr³⁺, MnO₄^-, and TNP are labeled with high selectivity and sensitivity, quick response, and good recyclability. It is anticipated that this MOF-based versatile sensor could shed light on the exploration of MOFs for fluorescent sensors, optical switches, etc.

Donor-Acceptor Compensated ZnO Semiconductor for Photoelectrochemical Biosensors

Hindering the recombination of a photogenerated carrier is a crucial method to enhance the photoelectrochemical performance of ZnO due to its high exciton binding energy. Herein, the intramolecular donor-acceptor compensated semiconductor ZnO (I-D/A ZnO), introducing C dopants and oxygen vacancies, was prepared with the assistance of ascorbic acid (AA). According to the DFT calculations, the asymmetry DOS could lead to the longer carrier lifetime and the smaller electron transfer resistance. Then, the photoelectrochemical biosensor toward glucose was regarded as a model to discuss the application of ZnO in biosensors. As a result, the biosensor based on I-D/A ZnO showed good performance with high sensitivity, low limit of detection, and fine anti-interference, meaning that I-D/A ZnO is a promising semiconductor for photoelectrochemical biosensors.

Crystalline Porous Materials for Nonlinear Optics

Crystalline porous materials have been extensively explored for wide applications in many fields including nonlinear optics (NLO) for frequency doubling, two-photon absorption/emission, optical limiting effect, photoelectric conversion, and biological imaging. The structural diversity and flexibility of the crystalline porous materials such as the metal-organic frameworks, covalent organic frameworks, and polyoxometalates provide numerous opportunities to orderly organize the dipolar chromophores and to systemically modify the type and concentration of these dipolar chromophores in the confined spaces, which are highly desirable for NLO. Here, the recent advances in the crystalline porous NLO materials are discussed. The second-order NLO of crystalline porous materials have been mainly devoted to the chiral and achiral structures, while the third-order NLO crystalline porous materials have been categorized into pure organic and hybrid organic/inorganic materials. Some representative properties and applications of these crystalline porous materials in the NLO regime are highlighted. The future perspective of challenges as well as the potential research directions of crystalline porous materials have been also proposed.

Two porous Ni-MOFs based on 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine showing solvent determined structures and distinctive sorption properties toward CO2 and alkanes

By regulating the solvent used for synthesis, two porous Ni-MOFs, namely {[Ni3(BTC)2(TPT)2/3(H2O)4.08(MeOH)0.92]·2DMF·0.5H2O·0.5MeOH}n (1) and {[Ni3(BTC)2(TPT)2(H2O)6]·6DMF}n (2) (H3BTC = 1,3,5-benzenetricarboxylic acid, TPT = 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine, DMF = N,N-dimethylformamide, and MeOH = methanol) were obtained. Compound 1 reveals a rigid 3D framework, while compound 2 shows a flexible 3-fold interpenetrated framework. Compound 1 exhibits a selective adsorption of CO2 due to the sieving effect of the rigid framework containing two types of cages with small apertures. Noteworthily, the flexible compound 2 displays an obviously guest-induced structural transformation. The desolvated compound 2 reveals a much higher capacity toward CO2 and n-C4H10 than those of N2 CH4, C2H6 and C3H8.

Four 3D Co(ii) MOFs based on 2,4,6-tris(4-pyridyl)-1,3,5-triazine and polycarboxylic acid ligands and their derivatives as efficient electrocatalysts for oxygen reduction reaction

Different aromatic polycarboxylic acids are employed as auxiliary ligands to give rise to structural diversities in Co(ii)-tpt (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine) frameworks. By introducing various secondary aromatic polycarboxylate anions, namely, biphenyl-3,4',5-tricarboxylic acid (H₃bpt), 1,3,5-benzenetricarboxylic acid (H₃btc) and 2,6-dimethyl pyridine-3,5-dicarboxylic acid (H₂dmdcpy) into the Co(ii)-tpt system (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), four new complexes [Co₃(tpt)₂(Hbpt)₃]·0.5DMDP (1) (DMDP = N,N' = dimethylpropyleneurea), [Co₃(btc)₂(tpt)(H₂O)₃]·3H₂O (2), [Co₂(btc)(tpt)₂Cl]·DMDP·1.5H₂O (3) and [Co(tpt)(dmdcpy)]·H₂O (4) were obtained. Complexes 1 and 2 reveal amazing 3D networks in which the polycarboxylate ligands and Co(ii) ions connect with each other to form regular 3D porous frameworks with 1D cylindrical channels partitioned by virtue of the tpt ligands. Complexes 3 and 4 exhibit unusual 3D frameworks constructed from the Co-polycarboxylate layers pillared by tpt ligands. In addition, compound 1 was chosen as a precursor to prepare Co, N-codoped porous carbon materials (denoted as CoNC) as an eletrocatalyst for oxygen reduction reactions. In particular, the effect of different nitrogen sources on the electrocatalytic performance of MOF derived carbon materials was investigated. We found that although different nitrogen-containing ligands have a certain effect on the electrocatalytic performance of the synthesized CoMOF derived carbon materials, the additional nitrogen source has a significant effect on it. CoNC-A derived from compound 1 exhibits greater limiting current density than that of a Pt/C catalyst, while CoNC-B derived from a mixture of compound 1 and dicyandiamide shows almost identical onset potential but remarkably more positive half-wave potential as well as higher limiting current density as compared to commercial Pt/C catalysts.

A window-space-directed assembly strategy for the construction of supertetrahedron-based zeolitic mesoporous metal-organic frameworks with ultramicroporous apertures for selective gas adsorption

Despite their scarcity due to synthetic challenges, supertetrahedron-based metal-organic frameworks (MOFs) possess intriguing architectures, diverse functionalities, and superb properties that make them in-demand materials. Employing a new window-space-directed assembly strategy, a family of mesoporous zeolitic MOFs have been constructed herein from corner-shared supertetrahedra based on homometallic or heterometallic trimers [M3(OH/O)(COO)6] (M3 = Co3, Ni3 or Co2Ti). These MOFs consisted of close-packed truncated octahedral cages possessing a sodalite topology and large β-cavity mesoporous cages (∼22 Å diameter) connected by ultramicroporous apertures (∼5.6 Å diameter). Notably, the supertetrahedron-based sodalite topology MOF combined with the Co2Ti trimer exhibited high thermal and chemical stability as well as the ability to efficiently separate acetylene (C2H2) from carbon dioxide (CO2).

Topological-Distortion-Driven Amorphous Spherical Metal-Organic Frameworks for High-Quality Single-Mode Microlasers

Metal-organic frameworks (MOFs) have recently emerged as appealing platforms to construct microlasers owing to their compelling characters combining the excellent stability of inorganic materials and processable characters of organic materials. However, MOF microstructures developed thus far are generally composed of multiple edge boundaries due to their crystalline nature, which consequently raises significant scattering losses that are detrimental to lasing performance. In this work, we propose a strategy to overcome the above drawback by designing spherically shaped MOFs microcavities. Such spherical MOF microstructures are constructed by amorphizing MOFs with a topological distortion network through introducing flexible building blocks into the growth environment. With an ultra-smooth surface and excellent circular boundaries, the acquired spherical microcavities possess a Q factor as high as ≈10⁴ and can provide sufficient feedback for high-quality single-mode lasing oscillations. We hope that these results will pave an avenue for the construction of new types of flexible MOF-based photonic components.

Novel silver(i) cluster-based coordination polymers as efficient luminescent thermometers

Two original Ag-based clusters with a multidentate N-containing organic linker have been constructed featuring temperature-dependent luminescence behavior.

Fluorescence visualization of cucurbit[8]uril-triggered dynamic host–guest assemblies

Dynamic assemblies of π-conjugated bispyridinium guests with cucurbit[8]uril in aqueous solution could be distinguished by real-time naked-eye observation of the resulting quantitative fluorescence emissions.

A Robust Mixed-Lanthanide PolyMOF Membrane for Ratiometric Temperature Sensing

Temperature sensors play a significant role in biology, chemistry, and engineering, especially those that can work accurately in a noninvasive manner. We adopted a photoinduced post-synthetic copolymerization strategy to realize a membranous ratiometric luminescent thermometer based on the emissions of two lanthanide ions. This novel mixed-lanthanide polyMOF membrane exhibits not only the integrity and temperature sensing behaviour of the Ln-MOF powder but also excellent mechanical properties, such as flexibility, elasticity, and processability. Moreover, the polyMOF membrane shows remarkable stability under harsh conditions, including high humidity, strong acid and alkali (pH 0-14), which allowed the mapping of temperature distributions in extreme circumstances. This work highlights a simple strategy for polyMOF membrane formation and pushes forward the further practical application of Ln-MOF-based luminescent thermometers in various fields and conditions.

Molecular- and Structural-Level Organic Heterostructures for Multicolor Photon Transportation

The rational design and the fine synthesis of organic heterostructures (OHSs) are the key steps toward integrated organic optoelectronics. Herein we have demonstrated a self-assembly approach of combining a molecular-level heterostructure with a structural-level heterostructure and regulating the noncovalent intermolecular interactions for the precise construction of OHSs: a vertical type of anthracene-TCNB heterostructure and a horizontal type of benzopyrene-TCNB heterostructure. The excellent structural compatibility and the low lattice mismatch rate of ∼5.8% between single-component microplates and cocrystal microwires allow anthracene and benzopyrene molecules to grow epitaxially on the cocrystal. Significantly, integrating the multicolor emission and the distinctive dimensional-dependent photon transportation properties of low-dimensional micro/nanostructures, the multicolor optical outputs are achieved via modulating the active/passive optical waveguides in OHSs. Our work exhibits the utilization of the multilevel heterostructure strategy, which boosts the rational design of OHSs for organic photonics.